This still makes me seethe. We have pip, poetry, conda, and more. The Python folks knew that multiple incompatible systems would arise from a grammar spec without a behavior spec. And here we are. Python doesn't do anything useful with the types, but third-parties are left to their own devices.
Function annotations were added as part of Python 3.0, with PEP 3107, proposed in 2006 [0]. The first public mypy commit was in 2012 [1], and originally it was using C++-style syntax (`list<Token> lex(str s):`). The `typing` module and the official use of function annotation for type hints came in 2014 with PEP 484 [2], inspired by mypy. The first pyright commit was in 2019 (with a lot of code in the third commit [3], possibly moved from the VSCode extension).
This still makes me seethe. We have pip, poetry, conda, and more. The Python folks knew that multiple incompatible systems would arise from a grammar spec without a behavior spec. And here we are. Python doesn't do anything useful with the types, but third-parties are left to their own devices.